This invention relates to an apparatus and method for converting thermal energy to mechanical energy utilizing a liquid working fluid which remains in liquid state in a closed fluid system throughout the entire cycle.
Heretofore, such as shown in U.S. Pat. Nos. 1,487,664 dated March 18, 1924 and 1,717,161 dated June 11, 1929, both to John F. J. Malone, a so-called Malone-type heat engine has been developed utilizing a liquid working fluid or thermodynamic medium. The heat engine shown by Malone has a heat exchanger or regenerator in which a liquid working fluid always flows in the same direction therethrough.
In a heat exchanger in which the working fluid is a liquid always flowing in the same direction, the quantity of liquid inside the heat exchanger is greater than the quantity of liquid outside the heat exchanger. When liquids move through efficient heat exchangers, an unusually high heat transfer efficiency is obtained as heat transfer elements heat and cool liquids quickly with a relatively small percentage of heat loss. Further, the expansion of liquids is greater than their compressibility which permits a relatively large change of pressure with a relatively small change in temperature. The maximum temperature of a liquid working fluid is substantially below the critical temperature as liquids near the critical temperature are very easily compressed.
U.S. Pat. No. 4,209,982 dated July 1, 1980 to Clyde T. Pitts discloses a fluid energy conversion system in which two opposed cylinders have a liquid working fluid therein and utilize Freon 11 as a second fluid for operation of the opposed cylinders. The Freon is utilized as a gaseous fluid in the cylinders and is mixed or used in combination with the working fluid which is water. A turbine is powered by the working fluid and may in turn, be used to drive an electrical generator or an irrigation pump. Thus, a conversion system is shown in which the thermal energy from the working fluid is utilized for driving a mechanical power output.
U.S. Pat. No. 4,283,915 dated August 18, 1981 to David P. McConnell is directed to a system for converting the thermal energy of warm water which is used as the working fluid into a high pressure hydraulic output flow utilized for driving a hydraulic motor. Banks of heat exchangers utilizing a plurality of heat exchange tubes and fluid pressure accumulators are connected to the output of the heat exchanger for driving a hydraulic motor.